ROUTES OF IFOSFAMIDE METABOLISM

异环磷酰胺（IFOS）及其异构体环磷酰胺（CPA）是 用于癌症的氧氮磷杂环类烷化剂 化疗 IFOS是最近批准的药物，而CPA已被 广泛用作抗肿瘤和免疫抑制剂， 过去30年 IFOS与CPA一样，也经历微粒体活化。 不像 CPA、IFOS具有N-脱烷基化代谢物，其可能包含主要的 某些患者的消除途径，可能包括 消除某些患者，并可能解释其不同的毒性 profile. 进一步了解IFOS药理学的局限性 和潜在的药物相互作用是缺乏方法来衡量其肿瘤 活性代谢物 该项目的具体目标包括：a）开发技术， 定量IFOS B）的代谢，以比较CPA的代谢 并确定对IFOS的处置有重大影响的因素 c）确定尿保护剂美司钠是否显著 改变由氧化代谢形成的细胞毒性IFOS的量， （d）表征IFOS在患者中的代谢。 研究氧氮磷杂环戊烷药理学的主要局限是 在环状结构中缺少发色团。 衡量IFOS的方法 其代谢物将涉及修改用于 注册会计师 我们以前使用薄层色谱法（TLC）测定， 测量CPA在动物和人类体内的代谢。 我们希望修改此 用于检测IFOS主要代谢产物的TLC分析。3H-IFOS 就是被利用 氯乙基侧链上的放射性标记与 内环氮原子将允许测量所有 除了丙烯醛和去氯乙基-环磷酰胺之外， 一 最近描述的CPA离子对HPLC方法将适用于IFOS 并与使用TLC方法获得的结果进行比较。 后 最佳方法被开发用于定量IFOS及其代谢 产品，人类研究将随之而来。 随着TLC或HPLC技术定量IFOS的发展， 代谢，影响CPA代谢的因素可以评估为 IFOS。 这些因素包括遗传P-450同工酶的影响 遗传模式和已知的各种P- 450种同工酶。 IFOS在雌性Sprague-Dawley大鼠中的代谢将 与缺乏代谢的雌性Dark Agglomerate大鼠相比， 细胞色素IID 6。 IFOS在离体灌流肝中的代谢 制剂将在抑制 细胞色素P-450，包括西咪替丁、SKF-525 A、甲吡酮和 酮康唑 谷胱甘肽清除剂，美司钠，用于 与IFOS联合使用，保护患者免受尿毒性IFOS 代谢产物丙烯醛。 美司钠是否改变IFO抗肿瘤的量 形成的代谢物将是这些模型评估的另一个因素。 在 体外微粒体IFOS活化将用于进一步鉴定 抑制机制。 当IFOS的代谢途径 在动物模型中使用HPLC和TLC方法进行定量，IFOS 药代动力学可以扩展到新诊断的癌症 患者 使用这些技术， IFOS和美司钠可以在人类中进行研究。

Ifosamide (IFOS) and its isomer, cyclophosphamide (CPA), are members of the oxazaphosphorine class of alkylating agents used in cancer chemotherapy. IFOS is a recently approved drug whereas CPA has been used extensively as an antitumor and immunosuppressant agent for the last 30 years. IFOS, like CPA, undergoes microsomal activation. Unlike CPA, IFOS has N-dealkylation metabolites which may comprise a major route of elimination for some patients and may comprise a major route of elimination for some patients and may account for its different toxicity profile. A limitation in further understanding the pharmacology of IFOS and potential drug interactions is a lack of method to measure its tumor active metabolites. The specific aims of this project include: a) developing techniques to quantitate the metabolism of IFOS b) to compare the metabolism of CPA to IFOS and identify factors significantly influencing IFOS' disposition c) to determine whether the uroprotective agent mesna, significantly alters the amount of cytotoxic IFOS formed by oxidative metabolism and (d to characterize IFOS' metabolism in patients. The major limitation in studying oxazaphosphorine pharmacology has been the lack of chromophore in the ring structure. Methods to measure IFOS an its metabolites will involve modifying a TLC and HPLC method used for CPA. We have previously used a thin-layer chromatography (TLC) assay to measure CPA's metabolism in animals and humans. We wish to modify this TLC assay for the detection of IFOS' major metabolic products. 3H-IFOS is to be used. The radiolabel on the chloroethyl side chain attached to the endocyclic nitrogen atom will allow for the measurement of all metabolites except for acrolein and dechloroethyl-cyclophosphamide. A recently described ion pair HPLC method for CPA will be adapted for IFOS and compared to results obtained using the TLC method. After the optimal methods are developed for quantitating IFOS and its metabolic products, human studies will follow. With the development of TLC or HPLC techniques to quantitate IFOS' metabolism, factors which affect CPA's metabolism can be evaluated for IFOS. These factors include the influence of genetic P-450 isoenzyme inheritance patterns and the influence of known inhibitors of various P- 450 isoenzymes. IFOS' metabolism in female Sprague-Dawley rats will be compared with metabolism in female Dark Agouti rats, which lack cytochrome IID6. The metabolism of IFOS by isolated perfused liver preparations will be measured in the presence of agents which inhibit cytochrome P-450 including cimetidine, SKF-525A, metyrapone and ketoconazole. The glutathione scavenging agent, mesna, which is used in combination with IFOS, protects patients from the urotoxic IFOS metabolite, acrolein. Whether mesna alters the amount of IFO antitumor metabolites formed will be another factor evaluated by these models. In vitro microsomal IFOS activation will be used to further identify mechanisms of inhibition. When IFOS' metabolic routes have been quantitated using the HPLC and TLC methodology in animal models, IFOS pharmacokinetics can then be extended to newly diagnosed cancer patients. Using these techniques, the potential interaction between IFOS and mesna can be studied in humans.